Method of preparing cyclic 1-2-amino-ketones



Patented Sept. 29, 1936 UNITED STATES PATENT OFFICE .METHOD OF PREPARING CYCLIC I-Z-AMINO-KETONES Peter Wilhelm Neber, Tubingen, Germany 3 Claims.

The present invention relates to a method of manufacturing keto-amino compounds from ketomethylene compounds.

It has been found from earlier researches that keto-arnino compounds can be obtained from keto-methylene compounds through the aromatic sulpho esters of the oximes of the keto-methylene compounds by subjecting the aromatic sulpho esters of the keto-methylene compounds to an alkaline saponification and then splitting up the saponification product with acid.

It has nowbeenfound that this method of production of 1,2-keto-amino compounds has a much wider field of application than could be foreseen, and more particularly it is possible according to this invention to produce cyclic 1,2- amino-ketones, i. e. cyclic compoundscontaining a keto group and an amino group in adjacent positions directly in a carbocyclic or heterocyclic ring. From'other researches it has become known that in the non'alkaline saponification of aromatic sulpho esters of'the oximes of cyclic keto-methylene-compounds, a splitting up of the ring occurs. This reaction which can be regarded as'a kind of Beckmann transformation leads to end substitut ed aliphatic acid esters. Thus for example by heating the p-toluene sulpho ester of a-tetralonoximes with alcohol on abomb tube a butyric acid ester substituted with the o-aminophenyl group in the position is obtained while upon alkaline saponification of the aromatic sulpho esters of the oximes of cyclic 1,2-keto-methylene compounds on the other hand the ring system remains intact and upon subsequent splitting up of the saponification product, cyclic 1,2-keto-amino compounds are directly obtained;

The individual steps of the operation according to the invention are as follows:

By known methods, starting with keto-methylene compounds, i. e. cyclic compounds containing the group --GO.CH2 in a 'carbocyclic or heterocyclic ring the corresponding oximes are produced. These oximes are then converted by meansof aromatic sulpho chlorides such for example as benzene sulpho chloride or p-toluene sulpho-chloride, into the corresponding benzene sulpho or p-toluenesulpho-esters; The methylene-ketoxime-ptcluene-sulpho esters are then subjected to an alkaline saponification advantageouslyfor example by causing a solution of potash in alcohol to act in the coldon the methyl:- eneketoxime-p-t'oluene sulpho ester, whereby the potassium salt of p-toluene sulphonic acid 1 separates and an intermediate product results which is split up by the action'of acids to salts 5 of the corresponding amino ketone. If the splitting up of the said intermediate product is carried out in the presence of alcohols,,the amino-ketone itself is not obtained but the acetalof the aminoketone.

In the reaction set out above which proceeds in several steps, the oxime' group is converted back into the carbonyl group whilst a CHNH2 group appears instead of the CH2 group adjacent to the oxime group.

The keto-amino-compounds obtainable according to the process of the present invention are suitable for numerous further conversions, thus for example by condensation of two molecules of the keto-amines, dihydrogenated pyrazines are obtained which can easily be oxidized to pyrazines themselves. Since in many cases the keto-methyh ene compounds serving as starting materials are relatively easily accessible, according to the present invention also reactive keto-amino compounds which are valuable forfurther syntheses are also easily accessible.

Originally it was assumed that the first stage of the reaction of the process according to the invention consisted of a Beckmann transformation. This assumption has been' found notto be correct and it has beenfound in a surprising manner that the anti-position of the hydroxyl group of the oxime to theadjacent methylene group is not necessary for carrying out the process 35 according to the invention. Surprisingly therefore the new process can be'carried' out also in such cases in which the hydroxyl group of the oxim-e is in the syn-position to the adjacent methylene group. Likewise it was not tobe foreseen that the process according to the invention could becarried out also'insuch' cases where a methyl group is adjacent tothe oxim-e group for example in the case ofacetophenone oxime.

It must be expressly emphasized that the process according to the invention does not proceed smoothly with other esters of oximes than the aromatic sulpho esters. When using other esters than the aromatic sulpho esters there result either quite different products or complicated re- 0 action mixtures. Likewise, as already explained, in the case of nonalkaline saponification of the aromatic sulpho esters, undesired secondary phenomena which cannot be supervised occur.

In order that the invention may be well understood the following examples are given by way of illustration only.

Example 1 1.5 g. a-hydrindone oxime are dissolved in 4 cc. of dry pyridine. 1.9 g. p-toluene sulpho chloride in 4 cc. of dry pyridine are gradually added to the ice-cold solution. After allowing to stand for 18 hours, crystals are obtained which after crystallization from'hot ethyl acetate melt with decomposition at 157 C. (yield 2.2 g. a-hydrindoneoxime-p-toluene sulpho ester).

A solution of 1.6 g. potassium in 20 cc. absolute alcohol is added at 0 C. within 20 minutes to a suspension of 12 g. of very finely divided p-toluene sulpho ester of a-hYdIlIldOllG oxime in 35 cc. absolute alcohol. The suspension is kept with frequent shaking for 2 hours at 0 C. and is then shaken for 4 hours on the machine. It is then sucked off from the separated toluene sulphonic acid potassium, the filtrate is poured into 150 cc. ether and twice shaken up each time with 40 cc. 2n hydrochloric acid. Upon concentrating the red colored acid solution in vacuo 5.3 g. of salt are obtained. Upon dissolving this salt in hot alcohol a.very dark red solution is obtained from which the yellow hydrochloric acid salt of p-amino-a-hydrindone crystallizes out which only decomposes abovev 240 C. The yellow picrate prepared from this salt decomposes at 150 C.

Example 2 A solution of 16.4 g. of p-toluene sulphochloride in 25 cc. of pyridine is gradually added below 0 C. to an ice cold finely divided suspension of 20 g. of

in 45 cc. of pyridine whereby a clear solution is produced. After standing for 15 hours in an ice chest the solution is poured with stirring into ice water. The oil first separating, solidifies rapidly upon inoculation. After dissolving the sulpho ester after this has been well washed with water on the suction filter and then dried from cold benzene petrol ether mixture, 29 g. of a product melting with decomposition at 107 C. are obtained.

23.2 g. of the sulphoester are suspended in finely dispersed condition in 75 cc. of absolute alcohol, treated at room temperature with a solution of 2.4 g. of potassium in 25 cc. of absolute alcohol, warmed to 40 C. whereupon the saponification of the ester commences and after 15 minutes with gradual self heating to C. it is completed. After cooling the solution is poured into 50 cc. of absolute ether, the liquor is sucked mi from the potassium salt of the p-toluene sulphonic acid, the filtrate is twice thoroughly shaken with 75 cc. of 2n hydrochloric acid and the hydrochloric acid solution is freed from ether and alcohol. After the solution has been made alkaline again with caustic soda it is washed out with ether and the ethereal solution is then dried over sodium sulphate. Upon distilling oif the ether in vacuo 12 g. of a red-yellow oil remain behind which is converted by dissolving in the calculated quantity of hydrochloric acid into the 5 strongly hygroscopic monochlorhydrate of the amino-ketone.

i C NH2 10 HzC O H /C\ /O C6H5 CH3 III H 15 Example 3 A solution of 5.7 g. of p-toluene sulphochloride 20 in 9 cc. of pyridine is added below 0 C. to a solution of 8.4 g. of

in 18 cc. of pyridine. The solution is then kept for 12 hours at 0 C. Upon stirring the solution into ice water an oil is obtained which solidifies upon inoculation after some time. The ester is well ground with water, filtered off, washed out 35 and dried. The yield is 12 g. After dissolving again out of cold benzene and petrol ether the ester melts with decomposition at 104-105 C.

10.7 g. of this ester are finely pulverized, suspended in 35 cc. of absolute alcohol, and treated at 40 C. with a solution of l g. potassium in 12 cc. of absolute alcohol. The saponification is completed after 20 minutes. The cooled solution is then poured into 250 cc. of absolute ether. After drawing off from the potassium salt of the p- 45 toluene sulphonic acid, the ethereal filtrate is twice shaken with 4.0 cc. of 2n hydrochloric acid and then with 20 cc. of water. After removing the ether and concentrating the hydrochloric acid solution, finally the hydrochloric acid salt 50 of the amino ketone CH: crystallizes out with a quantitative yield. This is strongly hygroscopic and is purified by precipitating the alcoholic solution with ether.

Example 4 A solution of 2.8 g. of potassium in 75 cc. of absolute alcohol is added at 0 C. within half an hour to a finely powdered suspension of 20.3 g. of p-toluene sulpho ester of acetophenone-oxime (syn-methyl form) in 50 cc. of absolute alcohol and the whole is shaken for two hours on the machine, sucked oif from the potassium salt of p-toluene sulphonic acid, the filtrate is treated with 300 cc. of ether and the ethereal solution is twice shaken each time with 50 cc. of 2n hydrochloric acid. Upon concentrating the hydrochloric acid solution in vacuo at about 30-40 C., 8.1 g. of the hydrochloric acid salt of w'-aminoacetophenone are obtained (theoretical yield 11.8 g.).

From this example can be seen the applicability of the process according to the invention to the so called syn forms of the oximes and moreover to such cases where the oxime group is adjacent to a methyl group.

Example 5 12 g. of propiophenone-oxime-p-toluene sulpho ester (produced from a solution of propiophenone-oxime in twice normal caustic soda and ptoluene sulphochloride at 0 C.) are suspended in 40 cc. of absolute alcohol and to this is added a potassium ethylate solution (1.6 g. of potassium in 15 cc. of absolute alcohol). This is then shaken for two hours at room temperature and the liquor is sucked off from the separated potassium salt of p-toluene sulphonic acid. The filtrate is then poured in 150 cc. of ether and the ethereal solution is twice thoroughly shaken each time with 40 cc. of Zn hydrochloric acid. Upon concentrating the acid solution under reduced pressure at 30-40 C., 5.7 g. of the colorless hydrochloric acid salt of a-amino propiophenone are obtained.

Example 6 10 g. of p-toluene sulpho ester of u-tetralone oxime are suspended in 30 cc. of absolute alcohol and treated with a potassium ethylate solution produced from 1.3 g. of potassium and 15 cc. of absolute alcohol. After shaking for half an hour on the machine the conversion is completed. The solution has then become green and p-toluene sulphonic acid potassium has separated. The solution is filtered off from the latter and is washed with absolute ether and the filtrate added to 200 cc. of absolute ether, if necessary filtered again and the whole four times shaken with 20 cc. of Zn hydrochloric acid. The solution is then col ored red. The acid extract is evaporated in vacuo at 30-40 C., the residue is taken up again in water and filtered free from undissolved matter and again the water is removed in vacuo at 30-40 C. The substance is now of a rose color and is dried in vacuo over solid sodium hydroxide. After successive washing with chloroform, ethyl acetate and acetone it is obtained almost colorless. The melting point of the NHaHCl is about 115 C. (with decomposition). 4.5 g. about 72%.

In applying the new process to the a-tetralone oxime therefore the corresponding keto-aminocompound is obtained whilst as explained above whilst operating according to Schroeter by the Beckmann transformation which occurs a splitting up of the ring takes place.

I claim:

1. A method of preparing p-amino a-hydrindone including the steps of subjecting the p-toluene sulpho ester of a-hydrindone oxime to alkaline saponification and decomposing the saponification product by means of an acid.

2. A method of preparing cyclic 1,2-amino ketones including the steps of preparing the corresponding p-toluene sulphonic esters of the cyclic ketoximes by the action of p-toluene sulphonic chloride on the oximes of cyclic 1,2-keto methylene compounds, subjecting the sulphonic esters to alkaline saponification and splitting up the saponification product by means of acid.

3. A method of preparing cyclic 1,2-amino ketones including the steps of treating oximes of cyclic 1,2-keto-methylene compounds in which the hydroxyl group of the oxime is in the syn position to the methylene group with p-toluene sulphonic chloride to produce the corresponding ptoluene sulphonic esters of the cyclic ketoximes, subjecting the sulphonic esters to alkaline saponification and splitting up the saponification product by means of acid.

PETER WILHELM NEBER.

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